How to properly initialize singleton in didFinishLaunchingWithOptions?

Question

iOS

Hello, I can’t figure out what the problem is:
there is the most common singleton implementation:

+ (User *)current {
    static User *singleton = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        singleton = [[User alloc] init];
    });
    return singleton;
}

when called in didFinishLaunchingWithOptions, it hangs on dispatch_once (...)
if transferred to viewDidload, then everything is fine Tell me
what to change to make it work
Thank you

Answer 1

Make sure that [[User alloc] init] does not call the same current method again, most likely you have a dead lock.